Research On Key Algorithms For Three-dimensional Configuration Measurement Based On Multi-core Optical Fibe

Fiber optic three-dimensional shape sensing technology has the characteristics and advantages of small sensor size,anti-electromagnetic interference,flexibility,implantability,etc.It has been a hot spot and cutting-edge technology in the research of three-dimensional bit-shape measurement of continuum robots and three-dimensional shape measurement of large structures,and has important applications in medical robotics,aerospace,and other fields.A core issue of fiber optic shape sensing is the three-dimensional bit shape reconstruction algorithm,whose performance directly determines the accuracy of structural three-dimensional shape measurement.In order to improve the measurement accuracy of fiber optic 3D shape sensing technology,this paper carries out the research of 3D shape reconstruction algorithm based on multi-core optical fiber to provide high precision algorithm for 3D bit shape reconstruction based on multi-core optical fiber.The main research work includes:(1)Research on 3D bit shape reconstruction algorithm based on coordinate conversion of multi-core fiber.Based on the structural characteristics of parallel multi-core optical fiber and strain sensing principle,we study the fiber strain sensing model;establish a highprecision strain measurement method based on deep learning model;use strain measurement data to study the fiber 3D bit shape reconstruction algorithm based on the geometric relationship of adjacent sensing points;derive the fiber 3D deformation parameter calculation equation,use the node coordinate system conversion method,establish the multicore fiber 3D bit shape reconstruction algorithm,and The algorithm is validated and the accuracy is verified.(2)A differential geometry-based 3D bit shape reconstruction algorithm for helical multicore fibers.The helical multi-core fiber structure characteristics and 3D deformation sensing principle are studied by Kirchhoff’s elastic rod theory,and the 3D deformation measurement twist angle compensation method is established for the helical fiber core structure;the differential geometry curve theory method is used to study the fiber 3D bit shape reconstruction algorithm based on Frenet frame and Bishop frame,and the 3D bit shape reconstruction algorithm of helical multi-core fiber is established and verified.The algorithm is validated and verified.(3)Experimental system design and validation of multi-core fiber 3D bit shape measurement.The experimental system is designed and integrated to measure the 3D bit shape of multi-core optical fiber in discontinuous curvature track,and to verify the validity and accuracy of the nearest neighbor interpolation method.The accuracy difference of reconstruction results is compared and analyzed to verify the effectiveness and accuracy of the algorithm.Through the above study,a high-precision 3D bit shape reconstruction algorithm for multi-core optical fiber is established.The results show that compared with the coordinate transformation-based reconstruction algorithm,the differential geometry-based 3D bit shape reconstruction algorithm has higher reconstruction accuracy,and the measurement accuracy is better than 3.198 mm when the helical multicore fiber is in the range of 100mm-200 mm curvature radius and 0-300 mm pitch.The results provide a basis for the algorithm of multicore fiber 3D bit shape measurement,which has promising applications in medical robotics and aerospace fields.